Devices for mixing and dispensing multi-component compounds for dental purposes, for example as impression compound, are known. Since the reaction of the components begins with the mixing, there is only a limited working time available after the start of dispensing of the compound. An impression compound, for example, must be placed in the mouth before the working time has expired. The second important time for the dentist is the hardening time. In the case of an impression compound, this is the time it is necessary to wait before the material can be removed from the mouth. Although experience does give the dentist some feel for the length of time the compound can be worked and for when the material has completely set, mistakes regarding the time interval that has elapsed are still possible, especially in the case of complex impressions, and these mistakes can lead to incorrect results, for example poorly fitting impressions, and consequently to unnecessary expenditure in terms of time and cost. The same applies to other applications. For example, when preparing temporary crowns or bridges, it is necessary to observe the gelling time in which the mixed compound is in an elastic phase and can thus still be removed from the undercut tooth stump. The invention affords the user a means giving more precise information regarding the times available to him. According to the invention, a timer for indicating times which are to be observed is connected to the device for dispensing multi-component compound.
A particularly advantageous embodiment of the invention is one in which the timer is automatically triggered as a function of the running of the dispensing device. This preferably occurs at the start and/or at the end of the delivery procedure. If the working time is to be displayed, i.e. the length of time which at each point in time is still available for working the material, the timer runs from the start of the delivery procedure. If the hardening time is to be displayed, i.e. the length of time after which the last-applied material has also hardened, the timer runs from the end of the delivery procedure. Since the delivery time can vary greatly between different working techniques, the two time intervals can be differently staggered in relation to each other. For example, the movement of a switch, with which the dispensing device is started up, can simultaneously start the timer for the working time. Correspondingly, using the switch with which the dispensing is ended, a second timer can be started up which displays the hardening time.
As regards the way in which the timer signals the time, recourse may be had to known display possibilities. For example, the time still remaining at each point in time until expiry of the working time or hardening time can be displayed in seconds or minutes. Alternatively, the length of time which has elapsed since the timer was started is displayed. Since the dentist should have the possibility of controlling the preset time interval in each case and of adjusting his work thereto, this time interval should be displayed before the delivery procedure has commenced. In many cases, one signal is sufficient for displaying the end of the set time, for example the working time or the hardening time. If the time concerned is one where it is necessary to do something before the said time has expired (working time, gelling time), the signal is given before the time has expired, so that the dentist still has time to act, or a preliminary signal is given before the signal which indicates the time has expired. If, by contrast, the expiry itself is relevant, only this need be signalled. The signal can be an acoustic one, for example, so that the dentist can give his full visual attention to the patient. The timer is preferably reset automatically to the initial status, i.e. to the preset time interval, after the display. In another variant, the timer is reset automatically to the initial status on each newly commencing delivery procedure.
If only compounds are ever to be worked having about the same duration of the relevant time interval or time intervals, the respective display interval of the timer can be preset by the manufacturer such that it cannot be altered. Instead of this, it is also possible for the time interval of the timer to be set by the user for each case of use. A further possibility is one in which although the time interval can be adjusted, the selected setting is stored so that it does not have to be selected again upon each use.
If compounds with different working, gelling and hardening times can be worked in one dispensing device, which compounds are fitted in the device in the form of exchangeable cartridges, it is particularly advantageous for the exchangeable cartridges and the device or the timer to be provided with interacting facilities for automatically setting the time interval to be given to the timer. To do this, it is possible, for example, to use the technique which is known for automatically setting the film sensitivity in cameras. The device is equipped with a facility for reading a bar code, punched code, color code or magnetic strip code provided on the cartridge. The code can be applied directly on the cartridge and can also be read directly from there. However, it is also possible to provide the code separately from the cartridge or container holding the material and to read the code at another point on the device. For example, it can be arranged on a packaging or on a control chip which is enclosed with the package and which delivers the desired control commands for the timer. With the code or with the chip, in whichever form it may be provided, other material-dependent functions of the device can also be controlled, for example the mixing speed, the delivery speed or the dispensing quantity. The latter, for example, can be predetermined by the timer as a function of the dispensing time. The automatic presetting of the display of the working time or hardening time should be able to be manually overridden in order to allow the user to adapt to different working conditions.